Compact display assembly

ABSTRACT

A compact display assembly includes a flexible display screen such as a passive LCD screen or an OLED display screen. Printed circuit boards including driving circuitry for the display screen are mounted at its rear in a configuration defining a longitudinal region of the screen about which it may be folded or curved over on itself to a compact configuration. The assembly may be included in electronic computational devices such as laptop computers, electronic books and the like.

FIELD OF THE INVENTION

The present invention relates to a compact display assembly. In aparticular embodiment the invention relates to a display assemblyincorporating a liquid crystal display (LCD) though other displays, suchas an organic light emitting diode (OLED) display might also be used.

DESCRIPTION OF RELATED ART

It is now possible to obtain LCD devices having substrates made of aflexible plate, for example a plastic film. Such devices may be mountedon non-planar surfaces. One such LCD is described in U.S. Pat. No.4,674,840 to Bennett. More recently, another flexible LCD device hasbeen described in U.S. Pat. No. 6,204,902 to Kim et al.

Considerable research is presently being undertaken in relation to thedevelopment of OLED displays. OLED displays are made according to amulti-layer process by which an extremely thin polymer layer issandwiched between two electrodes. A few layers of atoms from anindium-tin-oxide (ITO) transparent electric conductor are sputtered ontransparent, flexible carrier films to form an anode. The anode isspin-coated with a very thin layer of electroluminiscent polymers.Centrifugal forces distribute the polymers, liquefied by solvents, in anabsolutely uniform manner. In a final step a mechanically flexiblecathode, being a combination of various metals, is sputtered on thecomponent. The final product is flexible and less than 500 nm inthickness.

The manufacture of a display assembly which incorporates a flexibledisplay poses a number of problems. One problem is that while thedisplays are flexible they will be damaged or their operation will beimpaired if they are creased. Another difficulty is that although thedisplay is flexible the associated driving circuitry is most readilymounted on rigid printed circuit boards. Accordingly a number ofconnections must be made between a flexible display and one or morerigid circuit boards which presents difficulties.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a display assemblywhich incorporates a flexible display and which is arranged so that thedisplay may be folded or curved over on itself without creasing.

According to the present invention there is provided a display assemblyincluding:

-   -   a flexible display screen having a plurality of connection        points;    -   at least two printed circuit boards located at the rear of said        screen and defining a longitudinal region of the screen        therebetween; and    -   flexible connectors between connection points located in said        region and each of the printed circuit boards;    -   wherein the flexible connectors are of sufficient length to        accommodate closing of the assembly about the longitudinal        region.

The flexible connectors may comprise looms of wires.

It is preferred that the printed circuit boards connect to the looms ofwires by means of tape automated bonding films.

Typically the screen will be rectangular in shape with an edge of thescreen and edges of the PCBs defining triangles and the flexibleconnectors terminating along edges of the triangles.

Preferably said edge of the screen and edges of the PCBs define righttriangles with the flexible connectors terminating along hypotenuses ofthe triangles.

Preferably the printed circuit boards are shaped so that the sum of thelengths of the hypotenuses is equal to said length of the displayscreen.

The flexible connectors may terminate along edges of the printed circuitboard defining the longitudinal region of the screen.

In a preferred embodiment the screen comprises a flexible liquid crystaldisplay.

Alternatively the screen may comprise an organic light emitting diodedisplay.

The display assembly may be incorporated into a computational device,for example a laptop computer or electronic book.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is plan view of the front of a prior art display assembly.

FIG. 2 is a plan view of the rear of a prior art display assembly.

FIG. 3 is a plan view of the front of a display.

FIG. 4 is a plan view of the rear of a display assembly according to anembodiment of the present invention.

FIG. 5 is a perspective view of an assembly according to an embodimentof the present invention in a compact configuration.

FIG. 6 is a plan view of an assembly according to an embodiment of thepresent invention in a display configuration.

FIG. 7 is a plan view of the rear of a display assembly according to afurther embodiment of the present invention in a compact configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order that members of the public may understand how the presentinvention may be put into practice a preferred embodiment of theinvention will now be described.

A schematic view of a typical prior art passive matrix display assembly10 is shown in FIG. 1. The liquid crystal display 12 is designed todisplay dot pattern images. A plurality of row and column electrodes arehorizontally and vertically disposed across the liquid crystal display.Connection points for the electrodes are located along edges of theliquid crystal display.

Circuit boards 14 and 18 are coupled to the row and column electrodes ofthe LCD by means of tape automated bonding (TAB) films 22 and 24. PCB's14 and 18 support circuitry including a row driver chip and columndriver chip, 26 and 28 respectively, for applying potentials to selectedrow and column electrodes in order to selectively activate liquidcrystal cells to form a display. For mounting in an apparatus such as alaptop computer or mobile phone the printed circuit boards 18 and 14 maybe folded back behind the screen as shown in FIG. 2 which is a rear viewof the display assembly. It will be realized that flexing of the LCD 12would place a strain on the TAB connections 22, 24 to each of PCBs 14and 18.

A preferred embodiment of the present invention will now be describedwith reference to FIG. 3. FIG. 3 depicts a flexible LCD screen 30including TAB connections 32 and 34 for connecting to display rowelectrodes.

Beneath the lower edges of the flexible LCD 30 there are located twoangled TAB strips 36 and 38. Connection points on each of the angled TABstrips are connected to column electrodes of the LCD display by means offlexible wire looms 40 and 42 respectively. It may be noted that in thepresently described embodiment, the distance L1 along the TAB strip 36is equal to the distance L1 along the column electrodes to which it isconnected by wire loom 42. Accordingly the distance between the columnelectrodes is maintained as the distance between contacts on the TABstrip which may be desirable in some circumstances. The arrangement isidentical in respect of the left hand TAB strip 38 which has a lengthL2=L1.

FIG. 4 shows a rear view of the display of FIG. 3 with PCBs 44 and 46attached to the folded over TAB strips 32-38. It will be noted thatthere is sufficient width in the longitudinal region of the screen,defined by edges A-A′ and B-B′, of the PCBs for the display to be curvedor folded on itself without creasing. The bottom edge 41 of screen 30along with edge A-A′ of PCB 46 and TAB film 38 define a right triangle39. Similarly triangle 37 is defined by edge B-B′ of PCB 44 and TAB film36.

The display assembly is shown curved upon itself to a compactconfiguration in FIG. 5. Upon folding the screen as shown in FIG. 5 thewires connecting column electrode connection points in the regionbetween lines A-A′ and B-B′ (FIG. 3) to TAB strips 36 and 38 tighten.Accordingly a degree of slack must be present in those wires of looms 40and 42 when the assembly is in an open configuration as shown in FIG. 6.

Computational devices such as laptop computers, electronic books and thelike may be designed with a hinged or otherwise folding housing toincorporate the display assembly thereby facilitating formation of acompact device. A further embodiment of the invention is depicted inFIG. 7. FIG. 7 shows the rear of a display assembly in which the PCBs 54and 56 do not project from the bottom of the screen. Rather columnelectrode connection points 52 in the region between A-A′ and B-B′ areconnected to connection points 60 and 62 on the inner edges of PCBs 54and 56 by flexible connectors 58.

Variations of the invention other than the embodiments that have beendescribed with reference to FIGS. 3-7 are of course possible. Forexample other types of flexible display screen may be used such as anorganic light emitting diode screen. Furthermore, the connection betweenthe electrode contacts and the angled TAB films 38, 36 (FIG. 4) might bemade by means other than wire looms. For example a flexible film havingconductive traces upon it might be used to make the connections.Although the preferred embodiment has two printed circuit board defininga longitudinal flexing region of the screen it would also be possible toconstruct embodiments of the invention with other numbers of circuitboards.

While a preferred embodiment of the present invention has been describedin detail herein, it should be clearly understood that many variationsand/or modifications of the basic inventive concepts herein taught,which may appear to those skilled in the present art will still fallwithin the spirit and scope of the present invention as defined in theappended claims.

1. A flexible display assembly including: a flexible display screenhaving a plurality of connection points; at least two printed circuitboards located at the rear of said screen and defining a longitudinalregion of the screen therebetween; and flexible connectors betweenconnection points located in said region and each of the printed circuitboards; wherein the flexible connectors are of sufficient length toaccommodate closing of the assembly about the longitudinal region.
 2. Anassembly according to claim 1, wherein the flexible connectors compriselooms of wires.
 3. An assembly according to claim 2, wherein the printedcircuit boards connect to the looms of wires by means of tape automatedbonding films.
 4. An assembly according to claim 1, wherein an edge ofthe screen and edges of the PCBs define triangles and the flexibleconnectors terminate along edges of the triangles.
 5. An assemblyaccording to claim 4, wherein said edge of the screen and edges of thePCBs define right triangles with the flexible connectors terminatingalong hypotenuses of the triangles.
 6. An assembly according to claim 5,wherein the PCB's are shaped so that the sum of the lengths of thehypotenuses is equal to said length of the display screen.
 7. Anassembly according to claim 1, wherein the flexible connectors terminatealong edges of the printed circuit board defining the longitudinalregion of the screen.
 8. An assembly according to claim 6 or claim 7,wherein the screen comprises a flexible liquid crystal display.
 9. Anassembly according to claim 6 or claim 7, wherein the screen comprisesan organic light emitting diode display.
 10. A computational deviceincluding an assembly according to claim
 1. 11. A computational deviceincluding an assembly according to claim 6 or claim 7.